All known groups of fireballs contain bodies which may reach the Earths surface as meteorites and are of planetary origin. Since some fireballs have cometary orbits in the Solar System, then comets are probably of planetary origin. The possible explosion
of a large planet is discussed again. This time on the basis of gravitationally decelerated expansion of an originally superdense embryo.
This paper presents measurements of the polarization of light in the tails of the comets Arend-Roland and Mrkos, made in the total photographic light. Results given in Tables II and V indicate that the tail of the Arend-Roland comet contained a substantial dust component, while the polarization in the tail of the Mrkos comet can be explained predominantly by pure molecular emission.
This following paper discusses a method for determining the total mass of dust contained in the coma of a comet. On assumption of a certain frequency distribution of particle dimensions, and based on photometrical data, it arrives at the conclusion that the maximum total quantity of dust in the atmosphere of comets at the time of observation, amounts to 8 x 10^11 g. This value appears as the result from photometric parameters of the comets, which show strong continuous spectra and are therefore by the author supposed to yield a 1 : 1 relation between the brightnesses of the dust and gas components of the coma. The photometrical measurements of Comet Arend-Roland 1956h result in a maximum value of 1.4 x 10^11 g. The photometric measurement of the anomalous tail of Comet Arend-Roland arrives at 10^13 g as the maximum value of its mass.
Theories of the origin of the Oort ctoud are examined in the light of recent observations of comets and of star-forming environments, and some popular hypotheses are found to meet with difficulties. In particular chemical and experimental evidence that comets grow in an extremely cold, quiescent environment is proving difficult to reconcile with recent CO and IR observations showing that the environment of a star-forming region is characterised by turbulent,
high-velocity flows and that young stars are prone to recurrent, violent outbursts. The aggregation around young stars of
planetesimals pre-existing in molecular ciouds avoids these problems. However formed, the Oort cloud is disturbed through
interactions with its galactic environment. A record of these past disturbances, episodic or regular, is in principle recoverable through impact cratering and other geological signatures, and these terrestrial records therefore provide a further new constraint on the structure and evolution of the Oort cloud. The concepts of
r 'dense inner cloud' or a 'solar companion star' are difficult to reconcile with the impact cratering history. The debris from the very largest comets are expected to play a dominant role in producing galactic modulations of such fundamental phenomena as the rise and fali of oceans, ice ages, geomagnetic reversals and the origin of life. A ~15 Myr galactic cycle in particular is predicted. Power spectrum analyses applied to cratering, vulcanism and geomagnetic reversal records for the last -200 Myr reveal the presence of a 16 ± 2 Myr cycle.
Nine objective prism spectrograms by means of two cameras were achieved. It was impossible to point directly at the comet image by using the larger camera. The motions in α of both the camera and the comet were the same. The motion difference in δ was determined experimentally and introduced as correction. The photometrical tracings of the comet head and tail and of the stars were made by using a recording microphotometer. The computed dispersion curve was corrected by using the main comet head emissions. The identification of the emissions was done by a comparison with [2] and [3]. The spectrograms show strong CN and Na emissions. It was assumed, that the background below the emissions was due to continuous spectrum. Then its amplitude is nearly twice that of the emission lines. The amplitude ratio continuum/emission in the tail was 1 : 0·6. The spectrograms from the end of May show only weak C2 emissions. The tail directied towards the Sun was unobservable during our observations.
The study of one spectrum of comet Mrkos obtained on 1957 August 23 with an objective prism of dispersion 52 A/mm for λ 4000 A is given in this paper. and Článek doplňuje list se snímky komety (nestránkováno)